Present day digital computer systems typically include hundreds of integrated and discrete components mounted on one or more printed circuit boards (PCBs), the components located on a single printed circuit board being interconnected by wiring or circuits within the printed circuit board. These printed circuit boards may also include sockets and connectors for receiving additional components, signal cables, component modules, multi-chip modules and for connection to other printed circuit boards.
Computer memory, specifically RAM (Random Access Memory), often consists of one or more memory modules, such as SIMM (Single In-line Memory Module) boards which plug into special sockets on a main printed circuit board known as a motherboard, or a separate memory board. Each memory module may contain one, four or more megabytes of memory. Several memory module sockets are typically provided, not all of which are necessarily occupied. Thus the user can configure the memory system in accordance with the requirements of the computer system, and add additional memory modules, or larger capacity modules, should the memory demands of the system increase.
The printed circuit board memory module connector sockets are interconnected by a common set of address, data and control lines within the printed circuit board. However, as computer system speeds and memory requirements increase and more and more integrated devices are incorporated into printed circuit boards, computer main memory capacity and complexity have increased. Traditional memory packaging schemes are becoming inadequate as the disparity between on-chip memory speed and inter-chip communication speed increases. Additionally, as the speed of memory operations approaches 100 Mhz, an improved printed circuit board design is required to prevent undesirable transmission line effects.